Method for controlling sidelink HARQ feedback and device therefor

ABSTRACT

The present disclosure relates to a method and a device for providing a V2X service in a next generation radio access technology (new RAT). The present embodiments relate to a method for a terminal to control a sidelink HARQ feedback operation, the method comprising the steps of: receiving, from a transmitting terminal, group cast sidelink data through a physical sidelink shared channel (PSSCH); determining, on the basis of positional information of the transmitting terminal, whether to transmit HARQ feedback information of the group cast sidelink data; and, when it is determined to transmit the HARQ feedback information, transmitting the HARQ feedback information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Entry of PCT InternationalApplication No. PCT/KR2020/004872, which was filed on Apr. 10, 2020, andwhich claims priority from and the benefit of Korean Patent ApplicationNos. 10-2019-0043200, filed with the Korean Intellectual Property Officeon Apr. 12, 2019, 10-2019-0043283 filed with the Korean IntellectualProperty Office on Apr. 12, 2019, 10-2019-0077361 filed with the KoreanIntellectual Property Office on Jun. 27, 2019, 10-2019-0156725 filedwith the Korean Intellectual Property Office on Nov. 29, 2019,10-2020-0042185 filed with the Korean Intellectual Property Office onApr. 7, 2020, all of which are hereby incorporated by reference for allpurposes as if fully set forth herein. In addition, when thisapplication also claims priority for countries other than the UnitedStates for the same reason as above, all of the contents of theabove-listed applications are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a method and device for providing avehicle-to-everything (V2X) service in next generation wireless accesstechnology (New RAT).

BACKGROUND ART

There is demand for high-capacity data processing, high-speed dataprocessing, and a variety of services using a wireless terminal invehicles, industrial sites, and the like. Accordingly, there is demandfor technology for high-speed and high-capacity telecommunicationssystems grown out of simple voice-centric services and able to process avariety of scenarios and high-capacity data, such as images, wirelessdata, machine-type communication data, and the like.

In this regard, the ITU radiocommunication sector (ITU-R) disclosesrequirements for the adaptation of international mobiletelecommunications-2020 (IMT-2020) international standards. Researchinto next-generation wireless communication technology for meetingIMT-2020 requirements is underway.

In particular, in the 3rd generation partnership project (3GPP),research into LTE-Advanced Pro Rel-15/16 standards and new radio accesstechnology (NR) standards is underway in order to meet IMT-2020requirements referred to as 5G technology requirements. The two standardtechnologies are planned to be approved as next-generation wirelesscommunication technologies.

5G technology may be applied to and used in autonomous vehicles. In thisregard, 5G technology needs to be applied to vehicle-to-everything (V2X)communications. For autonomous driving, it is necessary to transmit andreceive increasing amounts of data at high speeds with high reliability.

In addition, both unicast data transmission and reception and multicastdata transmission and reception using vehicle communications must beprovided in order to meet variety of autonomous driving scenarios, suchas platooning. In particular, there is demand for a technology forhybrid automatic repeat request (HARD) operations for obtaining datatransmission reliability while reducing system load in sidelinkcommunications.

DISCLOSURE Technical Problem

Embodiments of the present disclosure may provide a method and devicefor performing sidelink communications using next-generation wirelessaccess technology.

Technical Solution

According to an aspect, provided is a method of controlling a sidelinkhybrid automatic repeat request (HARQ) feedback operation by a terminal.The method may include: receiving groupcast sidelink data from atransmitting terminal through a physical sidelink shared channel(PSSCH); determining whether or not to transmit HARQ feedbackinformation of the groupcast sidelink data in accordance with positioninformation of the transmitting terminal; and when it is determined totransmit the HARQ feedback information, transmitting the HARQ feedbackinformation.

According to another aspect, provided is a terminal for controlling asidelink HARQ feedback operation. The terminal may include: a receiverreceiving groupcast sidelink data from a transmitting terminal through aPSSCH; a controller determining whether or not to transmit HARQ feedbackinformation of the groupcast sidelink data in accordance with positioninformation of the transmitting terminal; and a transmitter transmittingthe HARQ feedback information when it is determined to transmit the HARQfeedback information.

Advantageous Effects

According to embodiments of the present disclosure, the method anddevice for performing sidelink communications using next-generationwireless access technology may be provided.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically illustrating a structure of an NRwireless communications system to which embodiments are applicable;

FIG. 2 is a diagram illustrating the frame structure in the NR system towhich embodiments of the present disclosure are applicable;

FIG. 3 is a diagram illustrating a resource grid supported by wirelessaccess technology to which embodiments of the present disclosure areapplicable;

FIG. 4 is a diagram illustrating a bandwidth part (BWP) supported bywireless access technology to which embodiments of the presentdisclosure are applicable;

FIG. 5 is a diagram illustrating an example synchronization signal blockin wireless access technology to which embodiments of the presentdisclosure are applicable;

FIG. 6 is a diagram illustrating a random access procedure in wirelessaccess technology to which embodiments of the present disclosure areapplicable;

FIG. 7 is a diagram illustrating a CORESET;

FIG. 8 is a diagram illustrating a variety of scenarios for V2Xcommunications;

FIGS. 9 a and 9 b illustrate an example of terminal 1 (UE1) and terminal2 (UE2) performing sidelink communications and an example of a sidelinkresource pool used by the terminals;

FIG. 10 is a diagram illustrating a method of bundling and transmittingHARQ feedback information in a sidelink;

FIG. 11 illustrates a method of performing at least one of activation(request), reactivation (re-request), and release or change of asemi-persistent scheduling (SPS) triggered by the terminal UE;

FIG. 12 is a diagram illustrating an example of a sidelinksynchronization signal block (S-SSB) allocated in an S-SSB monitoringslot according to an embodiment;

FIG. 13 is a diagram illustrating operations of a terminal according toan embodiment;

FIG. 14 is a diagram illustrating SCI received through a PSCCH accordingto an embodiment;

FIG. 15 is a diagram illustrating SCI received through a PSSCH accordingto an embodiment;

FIG. 16 is a diagram illustrating operations of calculating distanceinformation on the basis of the positions of a transmitting terminal anda terminal according to an embodiment;

FIG. 17 is a diagram illustrating operations of receiving the positioninformation of a transmitting terminal according to an embodiment;

FIG. 18 is a diagram illustrating operations of receiving the positioninformation of a transmitting terminal according to another embodiment;

FIG. 19 is a diagram illustrating position information of a transmittingterminal according to another embodiment; and

FIG. 20 is a diagram illustrating a configuration of a terminalaccording to an embodiment.

BEST MODE

Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the accompanying illustrativedrawings. In designating elements of the drawings by reference numerals,the same elements will be designated by the same reference numeralsalthough being shown in different drawings. Further, in the followingdescription of the present disclosure, detailed descriptions of knownfunctions and configurations incorporated herein will be omitted in thesituation in which the subject matter of the present disclosure may berendered rather unclear thereby. Terms such as “including”, “having”,“containing”, “constituting”, “make up of”, and “formed of” as usedherein are generally intended to allow other components to be addedunless the terms are used with the term “only”. As used herein, singularforms are intended to include plural forms unless the context clearlyindicates otherwise.

In addition, terms, such as first, second, A, B, (a), (b) or the likemay be used herein when describing components of the present disclosure.These terminologies are not used to define an essence, order, sequence,or number of corresponding components but used merely to distinguish thecorresponding components from other components.

In the case that it is described that two or more elements are“connected”, “coupled”, or “linked” to each other, such wording shouldbe interpreted as meaning the two or more elements may not only bedirectly “connected”, “coupled”, or “linked” to each other but also be“connected”, “coupled”, or “linked” to each other via another“intervening” element. Here, the other element may be included in one ormore of the two or more elements “connected”, “coupled”, or “linked” toeach other.

When temporally relative terms, such as “after”, “subsequent to”,“next”, “before”, and the like, are used to describe processes oroperations of elements or configurations, or flows or steps inoperating, processing, or manufacturing methods, these terms may be usedto describe non-consecutive or non-sequential processes or operationsunless the term “directly” or “immediately” is used together.

In addition, when any dimensions, relative sizes, etc. are mentioned, itshould be considered that numerical values for elements or features, orcorresponding information (e.g. level, range, etc.) include a toleranceor error range that may be caused by various factors (e.g. processfactors, internal or external impacts, noise, etc.) even when a relevantdescription is not specified.

The term “wireless communications system” used herein refers to a systemproviding a range of communication services, including voice and packetdata, using radio resources (or wireless resources). Such a wirelesscommunications system may include a terminal (or user equipment), a basestation, a core network, and the like.

Embodiments disclosed hereinafter may be used in wireless communicationssystems using a range of wireless access technologies. For example,embodiments may be used in a range of wireless access technologies, suchas code division multiple access (CDMA), frequency division multipleaccess (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier frequencydivision multiple access (SC-FDMA), or non-orthogonal multiple access(NOMA). In addition, wireless access technologies may mean not onlyspecific access technologies but also communications technologiesaccording to the generation, established by a variety of communicationsconsultative organizations, such as the 3rd generation partnershipproject (3GPP), the 3rd generation partnership project 2 (3GPP2), theWi-Fi alliance, the Bluetooth, the institute of electrical andelectronics engineers (IEEE), and the international telecommunicationunion (ITU). For example, CDMA may be realized by a wireless technology,such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe realized by a wireless technology, such as the global system formobile communications (GSM), General Packet Radio Service (GPRS), orenhanced data rates for GSM evolution (EDGE). OFDMA may be realized by awireless technology, such as IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802-20, or evolved-UMTS terrestrial radio access (E-UTRA, whereUMTS denotes the universal mobile telecommunications system). IEEE802.16m, evolved from IEEE 802.16e, provides backward compatibility withsystems based on IEEE 802.16e. UTRA is a portion of UMTS. 3rd generationpartnership project (LTE) long term evolution (3GPP) is a portion ofevolved UMTS (E-UMTS) using E-UTRA, and uses OFDMA in downlinks andSC-FDMA in uplinks. In this manner, embodiments of the presentdisclosure may be used in wireless access technologies that arecurrently disclosed or commercially available, or may be used in anywireless access technology currently being, or which will be, developed.

In addition, the term “terminal” used herein should be interpreted ashaving a comprehensive term referring to a wireless communicationsmodule that communicates with a base station in a wirelesscommunications system, and should be interpreted as including not only aterminal in wideband code division multiple access (WCDMA), LTE, newradio access technology (NR), HSPA, international mobiletelecommunications-2020 (IMT-2020; 5G or New Radio), and the like, butalso all of a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a wireless device, and the like, used in GSM. In addition,the terminal may refer to a user mobile device, such as a smartphone,depending on the type of use or may refer to a vehicle or a deviceincluding a wireless communications module in the vehicle in thevehicle-to-everything (V2X) communications system. Furthermore, in themachine type communications (MTC) system, the terminal may refer to anMTC terminal, a machine-to-machine (M2M) terminal, an ultra-reliabilityand low latency communications (URLLC) terminal, or the like, providedwith a communications module able to perform machine typecommunications.

The term “base station” or “cell” used herein refers to an end in anetwork, communicating with the terminal, and comprehensively indicatesa variety of coverage areas, such as a node-B, an evolved node-B (eNB),a gNodeB (gNB), a low power node (LPN), a sector, a site, an antennahaving a variety of shapes, a base transceiver system (BTS), an accesspoint, a point (e.g. a communication point, a reception point, or atransmission/reception point), a relay node, a megacell, a macrocell, amicrocell, a picocell, a femtocell, a remote radio head (RRH), a radiounit (RU), and a small cell. In addition, the cell may be understood asincluding a bandwidth part (BWP) in a frequency domain. For example, aserving cell may refer to an activation BWP of the terminal.

Since at least one of the variety of cells as stated above is controlledby a dedicated base station, the base station may be interpreted in twosenses. Each of the base stations 1) may be an apparatus itselfproviding a megacell, a macrocell, a microcell, a picocell, a femtocell,or a small cell in relation to a wireless communication area, or 2) mayindicate the wireless communication area itself. In 1), when apparatusesproviding wireless areas are controlled by the same entity orapparatuses interact with one another to form a wireless area in acoordinated manner, all of such apparatuses may be referred to as basestations. The transmission/reception point, the transmission point, thereception point, and the like are examples of the base station,according to the configuration of the wireless area. In 2), the wirelessarea itself in which a signal is received or transmitted may be referredto as a base station, from the perspective of a user or an adjacent basestation.

The term “cell” used herein may refer to a coverage of a signaltransmitted from the transmission point or the transmission/receptionpoint, a component carrier having the coverage of the signal transmittedfrom transmission point or the transmission/reception point, or thetransmission point or the transmission/reception point at which thesignal is transmitted.

The term “uplink (UL)” refers to a data transmission/reception method bywhich data is transmitted from the terminal to the base station, whereasthe term “downlink (DL)” refers to a data transmission/reception methodby which data is transmitted from the base station to the terminal. Thedownlink may refer to communications or a communication path from amultiple transmission/reception point to the terminal, whereas theuplink may refer to communications or a communication path from theterminal to the multiple transmission/reception point. In the downlink,a transmitter may be a portion of the multiple transmission/receptionpoint, whereas a receiver may be a portion of the terminal. In addition,in the uplink, the transmitter may be a portion of the terminal, whereasthe receiver may be a portion of the multiple transmission/receptionpoint.

The uplink and the downlink transmit and receive control information viaa control channel, such as a physical downlink control channel (PDCCH)or a physical uplink control channel (PUCCH), and transmit and receivedata by forming a data channel, such as a physical downlink sharedchannel (PDSCH) or a physical uplink shared channel (PUSCH).Hereinafter, transmitting or receiving a signal via a channel, such asthe PUCCH, the PUSCH, the PDCCH, or the PDSCH, may also be described as“transmitting or receiving the PUCCH, the PUSCH, the PDCCH, or thePDSCH”.

To clarify the description, the principle of the present disclosure willbe described with respect to 3GPP LTE/LTE-A/NR (New RAT) communicationssystem but the technical features of the present disclosure are notlimited to the corresponding communications system.

In 3GPP, 5th generation (5G) communications technology for meetingrequirements for next generation wireless access technology of theinternational telecommunication union radiocommunication sector (ITU-R)is developed. Specifically, in 3GPP, research on new NR communicationstechnology separate from LTE advanced Pro (LTE-A Pro) and 4Gtelecommunications technology improved from LTE Advanced in accordancewith the requirements of the ITU-R is developed. Both LTE-A Pro and NRrefer to 5G communications technology. Hereinafter, 5G communicationstechnology will be described with respect to NR, except that aparticular communications technology is specified.

In NR, a variety of operation scenarios are defined by addingconsiderations regarding satellites, vehicles, new vertical services,and the like to in typical 4G LTE scenarios. In terms of services, NRsupports an enhanced mobile broadband (eMBB) scenario; a massive machinecommunication (MMTC) scenario having high terminal density, deployedover a wide range, and requiring low data rates and asynchronousaccesses; and an ultra-reliability and low latency communications(URLLC) scenario requiring high responsiveness and reliability and ableto support high-speed mobility.

In order to meet the scenario described above, NR discloses a wirelesscommunications system using technologies providing a new waveform andframe structure, providing a low latency, supporting ultrahigh frequencywaves (mmWave), and providing forward compatibility. In particular, theNR system presents various technical changes in terms of flexibility inorder to provide forward compatibility. Major technical features of NRwill be described hereinafter with reference to the drawings.

<Principle of NR System>

FIG. 1 is a diagram schematically illustrating a structure of an NRwireless communications system to which embodiments of the presentdisclosure are applicable.

Referring to FIG. 1 , the NR system is comprised of a 5G core network(5GC) part and an NR-RAN part. The NG-RAN includes gNBs and ng-eNBsproviding protocol ends of a user plane (SDAP/PDCP/RLC/MAC/PHY) and acontrol plane (or a radio resource control (RRC)) for user equipment UE(or terminal). The gNBs are connected to each other, or the gNBs and theng-eNBs are connected to each other via an Xn interface. The gNBs andthe ng-eNBs are connected to each other via an NG interface in the 5GC.The 5GC may include an access and mobility management function (AMF)managing a control plane, such as terminal access and mobility control,and a user plane function (UPF) managing a control function over userdata. The NR system supports both a frequency range of 6 GHz or lower,i.e. frequency range 1 (FR1), and a frequency range of 6 GHz or higher,i.e. frequency range 2 (FR2).

The gNBs refer to base stations providing the NR user plane and controlplane protocol ends to the terminal, whereas the ng-eNBs refer to basestations providing evolved UMTS (E-UTRA) user plane and control planeprotocol ends to the terminal. The term “base station” used hereinshould be understood as comprehensively indicating the gNB and theng-eNB, or may be used as separately indicating the gNB and the ng-eNBas required.

<NR Waveform, Numerology, and Frame Structure>

In NR, cyclic prefix orthogonal frequency-division multiplexing(CP-OFDM) waveforms using the cyclic prefix (CP) for downlinktransmissions are used, and CP-OFDM or discrete Fourier transform spread(DFT-s)-OFDM is used for uplink transmissions. The OFDM technology hasadvantages in that the OFDM technology may be easily combined with amultiple-input multiple-output (MIMO) method, may have a high frequencyefficiency, and may use a low-complexity receiver.

In addition, in NR, requirements for data rate, latency, coverage, andthe like are different according to the above-described three scenarios.Thus, it is necessary to efficiently meet the requirements according tothe scenarios through frequency ranges of the NR system. In this regard,a technology for efficiently multiplexing a plurality of differentnumerology-based radio resources has been proposed.

Specifically, NR transmission numerology is determined on the basis ofsubcarrier spacing and the cyclic prefix (CP), and μ values areexponential values of 2 on the basis of 15 kHz and are exponentiallychanged, as described in Table 1 below.

TABLE 1 Subcarrier μ Spacing Cyclic Prefix Supported for Data Supportedfor Synch 0 15 Normal Yes Yes 1 30 Normal Yes Yes 2 60 Normal, Yes NoExtended 3 120 Normal Yes Yes 4 240 Normal No Yes

As described in Table 1 above, the numerology of NR may be divided intofive types according to the subcarrier spacing. This differs from thefeature of LTE, i.e. one of 4G communications technologies, in which thesubcarrier spacing is fixed to 15 kHz. Specifically, in NR, thesubcarrier spacings used for data transmissions are 15, 30, 60, and 120kHz, and the subcarrier spacings used for synchronous signaltransmissions are 15, 30, 12, and 240 kHz. In addition, an extended CPis only applied to 60 kHz subcarrier spacing. On the other hand, theframe structure in NR is defined as a frame having a length of 10 mscomprised of 10 subframes having the same lengths of 10 ms. A singleframe may be divided into 5 ms half frames, each of which includes fivesubframes. In the case of 15 kHz subcarrier spacing, a single subframecomprises a single slot, and each slot comprises fourteen OFDM symbols.FIG. 2 is a diagram illustrating a frame structure in the NR system towhich embodiments of the present disclosure are applicable.

Referring to FIG. 2 , the slot is constantly comprised of 14 OFDMsymbols in the case of a normal CP, but the length of the slot in thetime domain may vary depending on the subcarrier spacing. For example,when the numerology has the 15 kHz subcarrier spacing, the length of theslot is 1 ms, identical to that of the subframe. Differently thereto,when the numerology has the 30 kHz subcarrier spacing, the slot may becomprised of 14 OFDM symbols and have 0.5 ms length, such that two slotsmay be included in a single subframe. That is, each of the subframe andthe frame is defined having a fixed time length, and the slot may bedefined by the number of symbols, such that the time length may varydepending on the subcarrier spacing.

In addition, in NR, the slot is defined as a basic unit of thescheduling, and a mini-slot (or a sub-slot or a non-slot based schedule)is introduced in order to reduce a transmission delay in a wirelesssection. When a wide subcarrier spacing is used, the transmission delayin the wireless section may be reduced, since the length of a singleslot is shortened in inverse proportion thereto. The mini-slot (orsub-slot) is devised to efficiently support URLLC scenarios andscheduling on the basis of 2, 4, or 7 symbols may be possible.

In addition, unlike LTE, NR defines uplink and downlink resourceallocations as symbol levels in a single slot. In order to reduce hybridautomatic repeat request (HARQ) latency, a slot structure able todirectly transmit at least one of an HARQ acknowledgement (HARQACK) oran HARQ negative acknowledgement (HARQNACK) in a transmission slot isdefined. In the description, this slot structure will be referred to asa self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slotformats are used in 3GPP Rel-15. In addition, various slot combinationssupport a common frame structure including an FDD, or a TDD frame. Forexample, NR supports a slot structure in which all symbols of the slotare configured as downlinks, a slot structure in which all symbols ofthe slot are configured as uplinks, and a slot structure in whichdownlink symbols and uplink symbols are combined. In addition, NRsupports a form of scheduling in which data transmission is distributedin one or more slots. Accordingly, the base station may inform theterminal of whether a corresponding slot is a downlink slot, an uplinkslot, or a flexible slot, using a slot format indicator (SFI). The basestation may indicate a slot format by indicating an index of a table,configured by terminal-specific (UE-specific) RRC signaling, using theSFI, dynamically using downlink control information (DCI), or staticallyor quasi-statically through the RRC.

<NR Physical Resource>

Regarding the physical resources in NR, antenna ports, resource grids,resource elements (RE), resource blocks, bandwidth parts (BWPs), and thelike are considered.

The term “antenna port” is defined such that a channel carrying a symbolon an antenna port may be inferred from a channel carrying anothersymbol on the same antenna port. When the large-scale property of achannel carrying the symbol on one antenna port is inferable from achannel carrying a symbol on another antenna port, the two antenna portsmay be in a quasi co-located or quasi co-location (QC/QCL) relationship.Here, the large-scale property includes at least one of a delay spread,a Doppler spread, a frequency shift, average received power, andreceived timing.

FIG. 3 is a diagram illustrating a resource grid supported by wirelessaccess technology to which embodiments of the present disclosure areapplicable.

Referring to FIG. 3 , since NR supports a plurality of numerologies inthe same carrier, the resource grid maybe present according to eachnumerology. In addition, the resource grid may be configured dependingon the antenna port, the subcarrier spacing, and the transmissiondirection.

A resource block is comprised of 12 subcarriers and is only defined in afrequency domain. In addition, a resource element is comprised of oneOFDM symbol and one subcarrier. Therefore, as shown in FIG. 3 , the sizeof one resource block may vary depending on the subcarrier spacing. Inaddition, NR defines “point A” serving as a common reference point for aresource block grid, a common resource block, and a virtual resourceblock.

FIG. 4 is a diagram illustrating a BWP supported by wireless accesstechnology to which embodiments of the present disclosure areapplicable.

In the NR, the maximum carrier bandwidth is configured to be in therange from 50 MHz to 400 MHz depending on the subcarrier spacing, unlikein the LTE with the carrier bandwidth thereof being fixed to 20 MHz.Thus, it is not assumed that all terminals use all of these carrierbandwidths. Accordingly, as illustrated in FIG. 4 , in NR, a bandwidthpart (BWP) may be designated within a carrier bandwidth so as to be usedby the terminal. In addition, the BWP may be associated with onenumerology, be comprised of a contiguous subset of the common resourceblocks, and be dynamically activated over time. The terminal is providedwith up to four BWPs in each of an uplink and a downlink, and transmitsand receives data using an activated BWP at a given time.

In the case of a paired spectrum, the uplink and downlink BWPs areconfigured independently. In the case of an unpaired spectrum, theuplink BWP and the downlink BWP are configured in pairs such that thecenter frequency may be shared therebetween in order to preventunnecessary frequency re-tuning between downlink and uplink operations.

<Initial Access of NR>

In NR, the terminal performs cell search and random access procedures toaccess a base station and performs communications with the base station.

The cell search procedure is a procedure of synchronizing the terminalwith the cell of a corresponding base station using asynchronizationsignal block (SSB) transmitted from the base station, acquiring aphysical layer cell identifier (ID), and acquiring system information.

FIG. 5 is a diagram illustrating an example synchronization signal blockin wireless access technology to which embodiments of the presentdisclosure are applicable.

Referring to FIG. 5 , an SSB includes a primary synchronization signal(PSS) and a secondary synchronization signal (SSS), each of whichoccupies one symbol and 127 subcarriers, and a physical broadcastchannel (PBCH) covering three OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in time andfrequency domains.

The SSB may be transmitted up to 64 times for 5 ms. A plurality of SSBsare transmitted on different transmission beams within a period of 5 ms,and the terminal performs detection on the assumption that an SSB istransmitted at every 20 ms period, on the basis of a specific beam usedfor transmission. The number of beams that may be used for the SSBtransmission within the 5 ms period may increase with increases in thefrequency range. For example, up to four SSB beams may be transmitted ina frequency range of 3 GHz or lower. SSB may be transmitted using up toeight beams in a frequency range of 3 to 6 GHz and up to 64 differentbeams in a frequency range of 6 GHz or higher.

Two SSBs are included in one slot, and the start symbol and the numberof repetitions in the slot are determined depending on the subcarrierspacing as will be described later.

In addition, unlike an SS of related-art LTE, the SSB is not transmittedat the center frequency of a carrier bandwidth. That is, the SSB may betransmitted on a frequency that is not the center frequency of a systemrange, and a plurality of SSBs maybe transmitted in a frequency domainwhen a wideband operation is supported. Thus, the terminal monitors theSSBs using a synchronization raster that is a candidate frequencyposition for the monitoring of the SSBs. A carrier raster and thesynchronous raster, which are center frequency position information of achannel for initial access, are newly defined in NR. The synchronousraster is configured to have a wider frequency interval than the carrierraster, and thus, may support the terminal for rapid SSB search.

The terminal may acquire a master information block (MIB) through thePBCH of the SSB. The MIB includes minimum information by which theterminal receives remaining minimum system information (RMSI) broadcastby the network. In addition, the PBCH may include information regardingthe position of a first demodulation reference signal (DM-RS) symbol inthe time domain, information (e.g. system information block 1 (SIB1)numerology information, information regarding an SIB1 control resourceset (SIB1 CORESET), search space information, or PDCCH related parameterinformation) by which the terminal monitors SIB1, information regardingan offset between a common resource block and an SSB (where the absoluteposition of the SSB in the carrier is transmitted via SIB1), and thelike. Here, the SIB1 numerology information is equally applied to somemessages used in a random access procedure for accessing a base stationafter the terminal has completed the cell search procedure. For example,the SIB1 numerology information may be applied to at least one ofmessages 1 to 4 for the random access procedure.

The above-described RMSI may refer to system information block 1 (SIB1),which is periodically broadcast (e.g. at 160 ms) in the cell. SIB1includes information necessary for the terminal to perform an initialrandom access procedure and is periodically transmitted through thePDSCH. In order for the terminal to receive SIB1, the terminal isrequired to receive numerology information, which is used for SIB1transmission, and control resource set (CORESET) information, which isused for SIB1 scheduling, through the PBCH. The terminal reviewsscheduling information regarding SIB1 using a system information radionetwork temporary identifier (SI-RNTI) in the CORESET, and acquires SIB1on the PDSCH according to the scheduling information. The remaining SIBsother than SIB1 may be periodically transmitted or may be transmitted atthe request of the terminal.

FIG. 6 is a diagram illustrating a random access procedure in wirelessaccess technology to which embodiments of the present disclosure areapplicable.

Referring to FIG. 6 , when cell search is completed, the terminaltransmits a random access preamble, in use for random access, to thebase station. The random access preamble is transmitted through aphysical random access channel (PRACH). Specifically, the random accesspreamble is transmitted to the base station through the PRACH comprisedof consecutive radio resources in a predetermined slot periodicallyrepeated. In general, a contention-based random access procedure isperformed when terminal initially accesses a cell, whereas anon-contention based random access procedure is performed when randomaccess is performed for beam failure recovery (BFR).

The terminal receives a random access response to the transmitted randomaccess preamble. The random access response may include a random accesspreamble identifier (ID), an uplink (UL) radio resource grant, atemporary cell radio network temporary ID (temporary C-RNTI), and a timealignment command (TAC). Since one random access response may includerandom access response information regarding one or more sets ofterminal, the random access preamble ID may be included to order toindicate to which terminal the included UL grant, the temporary C-RNTI,and the TAC are valid. The random access preamble ID may be an ID of therandom access preamble that the base station has received. The TAC maybe included as information by which the terminal adjusts uplinksynchronization. The random access response may be indicated by a randomaccess ID on the PDCCH, i.e., a random access-radio network temporary ID(RA-RNTI).

When the valid random access response is received, the terminalprocesses information included in the random access response andperforms a scheduled transmission to the base station. For example, theterminal applies the TAC and stores the temporary C-RNTI. In addition,the terminal transmits data stored in a buffer or newly generated datato the base station, using the UL grant. In this case, information bywhich the terminal may be identified must be included.

Finally, the RA-RNTI receives a downlink message for contentionresolution.

<NR CORESET>

In NR, a downlink control channel is transmitted on a control resourceset (CORESET) having a length of 1 to 3 symbols. Up/down schedulinginformation, slot format index (SFI) information, transmit power controlinformation, and the like are transmitted through the downlink controlchannel.

Thus, in NR, in order to secure the flexibility of the system, theCORESET is introduced. The control resource set (CORESET) refers to atime-frequency resource for a downlink control signal. The terminal maydecode a control channel candidate using one or more search spaces in aCORESET time-frequency resource. Quasi colocation (QCL) assumption isestablished according to the CORESET. The QCL assumption is used inorder to inform the characteristics of analogue beam directions inaddition to characteristics assumed by related-art QCL, such as adelayed spread, a Doppler spread, a Doppler shift, or an average delay.

FIG. 7 is a diagram illustrating a CORESET.

Referring to FIG. 7 , the CORESET may have a variety of forms within acarrier bandwidth in a single slot. The CORESET may be comprised of upto three OFDM symbols in the time domain. In addition, the CORESET isdefined as a multiple of six resource blocks up to the carrier bandwidthin the frequency domain.

The first CORESET is a portion of an initial BWP configuration,indicated through the MIB so as to be able to receive additionalconfiguration information and system information from the network. Aftera connection to the base station is established, the terminal mayreceive and configure one or more pieces of CORESET information by RRCsignaling.

Herein, terms, such as frequency, frame, subframe, resource, resourceblock, region, band, sub-band, control channel, data channel,synchronization signal, various reference signals, various signals, orvarious messages, related to new radio access technology (NR) may beinterpreted as having a variety of meanings related to concepts used inthe past or present or which will be used in the future.

<Sidelink>

In existing LTE systems, wireless channels and wireless protocols havebeen designed for direct (i.e. sidelink) communications betweenterminals in order to provide direct terminal-to-terminal communicationsand V2X (in particular, V2V) services.

Regarding the sidelink, synchronization signals, e.g. a sidelink primarysynchronization signal (S-PSS) and a sideline secondary synchronizationsignal (S-SSS), for synchronization between a transmission port and areceiver port of the wireless sidelink and a physical sidelinkbroadcasting channel (PSBCH) for the transmission and reception of arelated sidelink master information block (MIB) are defined. Inaddition, a physical sidelink discovery channel (PSDCH) for transmissionand reception of discovery information, a physical sidelink controlchannel (PSCCH) for transmission and reception of sidelink controlinformation (SCI), and a physical sidelink shared channel (PSSCH) fortransmission and reception of sidelink data are designed.

In addition, technological developments, made for wireless resourceallocation (or radio resource allocation) for the sidelink, have beendivided into Mode 1, in which the base station allocates wirelessresources and Mode 2, in which the terminal performs allocation byselecting a wireless resource pool. In addition, the LTE system requiresadditional technological evolution in order to meet V2X scenarios.

In this environment, the 3GPP has deduced 27 service scenarios relatedto the recognition of a vehicle in the Rel-14 and determined majorperformance requirements according to road situations. In addition, inthe Rel-15, six performance requirements are determined by deducing moreadvanced 25 service scenarios, such as platooning, advanced driving, andlong-distance vehicle sensing.

In order to meet such performance requirements, technical developmenthas been carried out to improve the performance of conventional sidelinktechnology developed on the basis of D2D communications to comply withthe V2X requirements. In particular, for application to the cellular-V2X(C-V2X), a technology for improving a physical sidelink layer design tocomply with a high-speed environment, a resource allocation technology,and a synchronization technology may be selected as major researchtechnologies.

The sidelink to be described hereinafter may be construed ascomprehensively including links used in D2D communications developedafter 3GPP Rel-12, V2X communications after the Rel-14, and the NR V2Xafter the Rel-15. In addition, respective terms related to channels,synchronization, resources, and the like will be described as being thesame terms irrespective of the D2D communications requirements or theV2X Rel-14/15 requirements. However, for a better understanding,features of the sidelink meeting the V2X scenario requirements,different from the sidelink for D2D communications in the Rel-12/13,will mainly be described. Therefore, the terms related to the sidelinkto be described hereinafter are merely intended to describe D2Dcommunications, V2X communications, and C-V2X communications in adiscriminative manner in order to compare differences thereof and assistin the understanding thereof, but are not applied to a specific scenarioin a limitative manner.

<Resource Allocation>

FIG. 8 is a diagram illustrating a variety of scenarios for V2Xcommunications.

Referring to FIG. 8 , V2X terminals may be located inside or outside ofthe coverage of a base station eNB (or gNB or ng-eNB). (Although the V2Xterminals are illustrated as being vehicles, the V2X terminals may be avariety of devices, such as a user terminal.) For example,communications may be performed between terminals (UE N−1, UE G−1, andUE X) inside the coverage of the base station (or base station coverage)or between a terminal (e.g. UE G−1) inside the base station coverage anda terminal (e.g. UE N−2) outside of the base station coverage. Inaddition, communications may be performed between terminals (e.g. UE G−1and UE G−2) outside of the base station coverage.

In such a variety of scenarios, the allocation of wireless resources forcommunications is required so that the corresponding terminal performssidelink communications. The allocation of wireless resources isgenerally divided into an allocation method handled by the base stationand an allocation method selected by the terminal.

Specifically, the method in which the terminal allocates resources inthe sidelink includes a method in which the base station intervenes inthe selection and management of resources (Mode 1) and a method in whichthe terminal directly selects resources (Mode 2). In Mode 1, the basestation performs scheduling of a transmitting terminal about ascheduling assignment (SA) pool resource domain and a DATA pool resourcedomain allocated thereto.

FIGS. 9 a and 9 b illustrate an example of terminals UE1 and UE2performing sidelink communications and an example of a sidelink resourcepool used by the terminals.

Referring to FIGS. 9 a and 9 b , a base station is illustrated as beingan eNB, but may be a gNB or an ng-eNB. In addition, the terminals areillustrated as being cellular phones, but may be applied to a variety ofdevices, such as a vehicle or an infrastructure device.

In FIG. 9 a , the transmitting terminal UE1 may select a resource unitcorresponding to a predetermined resource from a resource poolindicating a set of resources and transmit a sidelink signal using thecorresponding resource unit. The receiving terminal UE2 may have theresource pool, which the transmitting terminal UE1 may transmit,configured therein and detect the signal transmitted by the transmittingterminal.

Here, when the terminal UE1 is inside the base station coverage, theresource pool may be informed by the base station. When the terminal UE1is outside of the base station coverage, the resource pool may beinformed by another terminal or may be determined to be a predeterminedresource. In general, the resource pool is comprised of a plurality ofresource units, and each terminal may select one or more resource unitsand use the selected resource units when transmitting sidelink signals.

Referring to FIG. 9 b , it may be appreciated that a total of NFXNTnumber of resource units are defined, with entire frequency resourcesbeing divided into NF number of frequency resource units, and timeresources being divided into NT number of time resource units. Here, thecorresponding resource pool may be regarded as being repeated in aperiod of an NT subframe. In particular, as illustrated in the figures,a single resource unit may repeatedly appear in a periodic manner.

In addition, the resource pools may be divided into a plurality oftypes. First, the resource pools may be divided according to contents ofsidelink signals transmitted by respective resource pools. For example,the contents of the sidelink signals may be divided, and separateresource pools may be configured therefor, respectively. The contents ofthe sidelink signals may include scheduling assignment (SA), a sidelinkdata channel, and a discovery channel.

The SA may be a signal including information regarding the position of asource that the transmitting terminal uses for the transmission of asubsequent sidelink data channel, a modulation and coding scheme (MCS)or multiple-input multiple-output (MIMO) transmission method requiredfor the modulation of other data channels, timing advance (TA), and thelike. This signal may be multiplexed and transmitted together withsidelink data on the same resource unit. In this case, the SA resourcepool may refer to a pool of resources via which the SA is multiplexedand transmitted together with sidelink data.

In addition, a frequency division multiplexing (FDM) method used in V2Xcommunications may reduce a delay time by which a data resource isapplied after SA resource allocation. For example, a non-adjacent methodby which control channel resources and data channel resources aredivided on the time domain in a single subframe and an adjacent methodby which control channel resources and data channel resources areconsecutively allocated in a single subframe are considered.

In addition, in a case in which the SA is multiplexed and transmittedtogether with the sidelink data on the same resource unit, only thesidelink data channel, from which SA information is excluded, may betransmitted in the resource pool for the sidelink data channel. In otherwords, resource elements that have been used to transmit the SAinformation on individual resource units in the SA resource pool maystill be used in the sidelink data channel resource pool to transmit thesidelink data. The discovery channel may be a resource pool for amessage with which the transmitting terminal transmits information, suchas the ID thereof, thereby allowing an adjacent terminal to discover thetransmitting terminal. Even in a case in which the contents of thesidelink signal are the same, different resource pools may be usedaccording to transmission and reception properties of the sidelinksignal.

For example, even the same sidelink data channels or the same discoverymessages may be subdivided into different resource pools, according tohow to determine a point in time at which the sidelink signal istransmitted (e.g. whether the sidelink signal is transmitted at a pointin time at which a synchronization reference signal is received or at apoint in time obtained by applying a predetermined TA to the point intime at which the synchronization reference signal is received), aresource allocation method (e.g. whether the base station designatestransmission resources of individual signals to individual transmittingterminals or individual transmitting terminals directly selectindividual signal transmission resources within the pool), a signalformat (e.g. the number of symbols that each sidelink signal occupies ina single subframe or the number of subframes used in the transmission ofa single sidelink signal), the intensity of a signal from the basestation, the intensity of transmission power of the sidelink terminal,and the like.

<Synchronization Signal>

As described above, it is highly possible that the sidelinkcommunications terminal may be located outside of the base stationcoverage. Even in this case, communications using the sidelink must beperformed. In this regard, it is important that the terminal locatedoutside of the base station coverage obtains synchronization.

Hereinafter, a method of determining time and frequency synchronizationin sidelink communications, in particular, vehicle-to-vehiclecommunications, communications between a vehicle and another terminal,and communications between a vehicle and an infra network, will bedescribed on the basis of the above description.

D2D communications have used a sidelink synchronization signal (SLSS),i.e. a synchronization signal that a base station transmits for timesynchronization between terminals. In the C-V2X, the global navigationsatellite system (GNSS) may be additionally considered in order toimprove synchronization performance. However, priority may be impartedto synchronization establishment, or the base station may indicateinformation regarding priority. For example, when the terminaldetermines the transmission synchronization thereof, the terminal hashighest priority in selecting a synchronization signal that the basestation directly transmits. When the terminal is located outside of thebase station coverage, the terminal has priority in synchronizing withthe SLSS that a terminal inside the base station coverage.

In addition, a wireless terminal disposed in a vehicle or a terminalmounted on a vehicle has a less problem related to the consumption ofthe battery. In addition, since satellite signals, e.g. signals of theglobal positioning system (GPS), may be used for navigation, thesatellite signals may be used for time or frequency synchronizationbetween terminals. Here, the satellite signals may be signals of aglobal navigation satellite system (GNSS), such as GLONAS, GALILEO, orBEIDOU, in addition to the GPS.

In addition, the sidelink synchronization signals may include a sidelinkprimary synchronization signal (S-PSS) and a sideline secondarysynchronization signal (S-SSS). The S-PSS may be a Zadoff-chu sequencehaving a predetermined length, a structure similar to, modified from, orobtained by repeating the PSS, or the like. In addition, unlike a DLPSS, a different Zadoff-chu root index (e.g. 26 or 37) may be used. TheS-SSS may be an M-sequence, a structure similar to, modified from, orobtained by repeating the SSS, or the like. If the terminals obtainsynchronization with the base station, an SRN is the base station, and asidelink synchronization signal (S-SS) is a PSS/SSS.

Unlike the DL PSS/SSS, the S-PSS/S-SSS is compliant with a UL subcarriermapping method. A physical sidelink broadcast channel (PSBCH) may be achannel through which system information, i.e. basic information that isthe first thing which the terminal must be informed of, is transmittedbefore the transmission or reception of the sidelink signal. (Examplesof the system information may include information regarding the S-SS,information regarding a duplex mode (DM), information regarding a TDDUL/DL configuration, information regarding the resource pool, types ofapplications related to the S-SS, subframe offset information, andbroadcast information.) The PSBCH may be transmitted on a subframe thesame as or subsequent to that of the S-SS. A demodulation referencesignal (DMRS) may be mused for the demodulation of the PSBCH. The S-SSand the PSBCH may be described as being a sidelink synchronizationsignal block (S-SSB).

The SRN may be a node through which the S-SS and the PSBCH aretransmitted. The S-SS may have a predetermined sequence type, while thePSBCH may be a sequence indicating predetermined information or a codeword obtained after predetermined channel coding. Here, the SRN may bethe base station or a predetermined sidelink terminal. In the case of apartial network coverage or out-of-network coverage, a terminal may bethe SRN.

In addition, the S-SS may be relayed for sidelink communications with anout-of-coverage terminal as required or may be relayed by multi-hoprelay. In the following description, relaying the synchronization signalrefers to not only directly relaying the synchronization signal of thebase station but also transmitting a sidelink synchronization signalhaving a separate format at a point in time at which the synchronizationsignal is received. Since the sidelink synchronization signal is relayedin this manner, a terminal inside the coverage and a terminal outside ofthe coverage may directly communicate with each other.

<NR Sidelink>

As described above, there is a demand for V2X technology based on NR inorder to meet complicated requirements such as autonomous driving,unlike the V2X based on the LTE system.

In the NR V2X, the frame structure of NR, a numerology, a channeltransmission and reception procedure, and the like are applied so thatmore flexible V2X services may be provided in a more variety ofenvironments. In this regard, the development of a technology forsharing resources between the base station and the terminal, a sidelinkcarrier aggregation (CA) technology, a partial sensing technology for apedestrian terminal, sTTI, and the like is required.

The NR V2X is designed to support not only broadcast used in the LTEV2X, but also unicast and group-cast. In this case, target group IDs areused for the group-cast and the unicast, but whether or not to use asource ID will be discussed later.

In addition, since the HARQ is to be supported for quality of service(QoS), the control information further includes an HARQ process ID. Inthe LTE HARQ, the PUCCH for the HARQ is transmitted after four subframesafter downlink transmission. In contrast, in the NR HARQ, feedbacktiming, e.g. PUCCH resources and feedback timing, may be indicated usinga PUCCH resource indicator or an HARQ feedback timing indicatorregarding the PDSCH in DCI format 1_0 or 1_1.

FIG. 10 is a diagram illustrating a method of bundling and transmittingHARQ feedback information in a sidelink.

Referring to FIG. 10 , in the LTE V2X, separate HARQ ACK/NACKinformation is not transmitted in order to reduce system overhead. Inaddition, according to selection, the transmitting terminal mayretransmit data one time for data transmission reliability. However, theNR V2X may transmit the HARQ ACK/NACK information in terms of datatransmission reliability. In this case, the corresponding informationmay be bundled and transmitted in order to reduce overhead.

That is, when the transmitting terminal UE1 transmits three sets of datato the receiving terminal UE2 and the receiving terminal responsivelygenerates HARQ ACK/NACK information, the HARQ ACK/NACK information maybe bundled and transmitted through the PSCCH. Although the HARA ACK/NACKis illustrated as being transmitted through the PSCCH in FIG. 10 , theHARA ACK/NACK may be transmitted through a separate channel or adifferent channel. The bundled HARQ information may be configured to be3 or less bits.

In addition, in FR1 for a frequency domain of 3 GHz or lower, 15 kHz, 30kHz, 60 kHz, and 120 kHz are determined to be discussed as a candidategroup for subscriber spacing (SCS). In addition, in FR2 for a frequencydomain higher than 3 GHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz aredetermined to be discussed as a candidate group for the SCS. In the NRV2X, mini-slots (e.g. symbols 2, 4, and 7) smaller than 14 symbols maybe supported as a minimum scheduling unit.

As an RS candidate group, DM-RS, PT-RS, CSI-RS, SRS, and AGC trainingsignals will be discussed.

Sidelink UL SPS

In general, UL transmissions using SPS may cause a slight delay whenthere is a significant gap between the generation of user data and aconfigured semi-persistent scheduling (SPS) resource. Thus, when the SPSis used in a traffic, such as a sidelink communication traffic,sensitive to a delay, an SPS scheduling interval must be small enough tobe able to support delay requirements.

However, since the terminal UE may not be able to sufficiently use theconfigured SPS resource, a smaller SPS scheduling interval may lead togreater overhead. Thus, the gap between the generation of user data andthe configured SPS resource must be insignificant, and the SPSscheduling interval must be appropriate to meet delay requirements. Atpresent, there is no mechanism supporting this function.

Accordingly, FIG. 11 illustrates a method of performing at least one ofactivation (request), reactivation (re-request), and release or changeof an SPS triggered by the terminal UE.

A terminal UE may receive an SPS configuration for at least onepredetermined logic channel. The terminal UE may receive the SPSconfiguration for the predetermined logic channel via systeminformation, an RRC connection configuration message, an RRC connectionreconfiguration message, or an RRC connection release message.

When data for at least one predetermined logic channel is usable, theterminal may transmit an SPS activation request to an eNB and perform ULtransmission using the configured SPS resource in response to an SPSactivation command received from the eNB. The terminal UE may transmitthe SPS activation request to the eNB through a physical uplink controlchannel (PUCCH), a MAC control element (CE), or an RRC message. That is,the terminal may transmit the SPS activation request to the eNB using acontrol resource used when requesting SPS activation. The controlresource may be a PUCCH resource, a random access resource, or a new ULcontrol channel resource. In addition, the terminal UE may transmit theSPS activation request to the eNB, for example, during RRC connectionestablishment or establishment, during handover, after handover, or atRRC_CONNECTED.

In the presence of UL data to be transmitted, the terminal UE activelyrequests the SPS activation from the eNB. Thus, the gap between thegeneration of the UL data and the configured SPS resource may bereduced.

Referring to FIG. 11 , the terminal receives SPS configurationinformation including three SPS configurations from the eNB. In thepresence of UL data to be transmitted from a higher layer, the terminaltransmits an SPS request message to the eNB through, for example, theMAC CE. The eNB sends an acknowledgement (ACK) message regarding one ofthe three SPS configurations. The terminal UE transmits UL data based ona predetermined resource, e.g. in a period of 1 sec, according to thecorresponding SPS configuration.

In addition, in the presence of UL data to be transmitted from thehigher layer at a predetermined point in time, the terminal UEretransmits the SPS request message to the eNB, for example, through theMAC CE. The eNB sends an acknowledgement message regarding another oneof the three SPS configurations. The terminal UE transmits UL datathrough a predetermined resource, e.g. in a period of 100 sec, accordingto the corresponding SPS configuration.

In addition, S-SS id_net is a set of S-SS IDs selected from amongphysical layer SLSS IDs {0, 1, . . . , and 335}, used by terminals thathave selected the synchronization signal of the base station as asynchronization reference. S-SS id_net may be {0, 1, . . . , and 167}.In addition, S-SS id_oon is a set of S-SS IDs that terminals outside ofthe base station coverage use when directly transmitting asynchronization signal. S-SS id_oon may be {168, 169, . . . , and 335}.

As described above, resource allocation, time synchronization setting,reference signal transmission, and the like are performed independentlyor in concert with the base station in terminal-to-terminal sidelinkcommunications, unlike in related-art signal transmission and receptionbetween a base station and a terminal.

In particular, in the case of next-generation wireless access technology(including terms, such as NR and 5G), a plurality of protocols betweenthe base station and the terminal are added or modified. Accordingly, inNR technology-based sidelink communications, a variety of protocols arerequired to be newly developed, unlike related-art LTE-based V2Xcommunication protocols.

The present disclosure is intended to propose operations, such as asynchronization signal receiving operation, resource allocation, andPSCCH, PSSCH, and DMRS configuration, in sidelink communicationsperformed between a transmitting terminal and a receiving terminal.Although embodiments will be described hereinafter with respect tosidelink communications, the embodiments may be equally applied to C-V2Xcommunications and D2D communications, as described above.

In NR, in response to changes in the subcarrier spacing (SCS) in an OFDMsystem, changes in the frame structure of a sidelink to be used whentransmitting and receiving information in sidelink communications arealso required.

In a CP-OFDM waveform and a DFT-s-OFDM waveform, the sidelink signal inembodiments may use the CP-OFDM waveform. In addition, the sidelink mayuse SCS as will be described later. For example, in frequency range (FR)1 using a frequency range of 6 GHz or lower, SCSs of 15 kHz, 30 kHz, and60 kHz are used. Here, the sidelink may be configured to mainly use the60 kHz spacing exhibiting best performance. In FR 2 using a frequencyrange of 6 GHz or higher, 60 kHz and 120 kHz are used, and 60 kHz maymainly be used.

In addition, the sidelink uses a cyclic prefix (CP) in order to preventdemodulation that would otherwise occur during transmission andreception procedures in wireless communications. The length of the CPmay be set to be the same as the length of the normal CP of an NR Uuinterface. An extended CP may be used as required.

In this situation, the synchronization signal, resource allocation, andeach sidelink channel structure of the sidelink need to be configured inconsideration of efficiency.

First, the configuration of a demodulation reference signal (DMRS)included in the PSSCH transmitted when the terminal performs sidelinkcommunications will be described.

The transmitting terminal may perform an operation of receivinginformation regarding one or more DMRS patterns and a resourceinformation set including information regarding one or more sidelinkresources.

In the case of sidelink communications, two types of resource allocationmodes may be configured. For example, in Mode 1, the transmittingterminal requests sidelink wireless resource allocation from the basestation and performs sidelink communications using a sidelink wirelessresource allocated by the base station. In Mode 2, the base stationallocates a resource information set, i.e. information regarding one ormore sidelink wireless resources, to the sidelink terminal in advance,and the terminal performs sidelink communications by selecting asidelink wireless resource from the allocated resource information set.Although the operations will be described as being set to Mode 2 in FIG.12 , the present disclosure is not limited thereto.

The resource information set and the information regarding one or moreDMRS patterns may be received by higher layer signaling. For example,the transmitting terminal or a receiving terminal located inside thecoverage of the base station receives the resource information setincluding one or more sidelink resources, to be used in sidelinkcommunication, by RRC signaling. In addition, at least one of thetransmitting terminal and the receiving terminal may receive theinformation regarding one or more DMRS patterns for sidelinkcommunication from the base station. The transmitting terminal and thereceiving terminal may respectively configure the resource informationset and DMRS pattern information therein by receiving the sameinformation.

In addition, the information regarding one or more DMRS patterns may bemapped according to the resource information set or the sidelinkresources. For example, when a first resource information set includingone or more pieces of resource information and a second resourceinformation set including one or more pieces of resource information areindicated by the base station, information regarding a single first DMRSpattern for the first resource information set and information regardinga single second DMRS pattern for the second resource information set maybe indicated by being mapped to the resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped according to respective sidelink resources included in a singleresource information set. Alternatively, the DMRS pattern informationmay be indicated by being mapped according to two or more sidelinkresource sub-sets included in a single resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped to respective groups obtained by grouping two or more resourceinformation sets. In addition, the sidelink resources and the DMRSpatterns may be indicated by being mapped in a variety of forms. Thetransmitting terminal configures the received resource information setand the received DMRS patterns therein.

The transmitting terminal may perform an operation of selecting a singlesidelink resource, via which sidelink communication is performed, on thebasis of the resource information set. When sidelink communication istriggered, the transmitting terminal selects a predetermined sidelinkresource from the configured resource information set. A method by whichthe terminal selects the predetermined sidelink resource from theconfigured resource information set for sidelink communication may beperformed according to a variety of standards. For example, thetransmitting terminal may select the predetermined sidelink resourceaccording to priorities allocated to a plurality of sidelink resources.Alternatively, the terminal may detect whether or not each of theplurality of sidelink resources is used and select a sidelink resourcehaving a detection result value equal to or smaller than a referencevalue. That is, the transmitting terminal may select a sidelink resourceto use by detecting sidelink resources, each of which is not used or isused less.

The transmitting terminal may perform an operation of selecting apredetermined DMRS pattern from the information regarding one or moreDMRS patterns on the basis of the selected sidelink resource. Forexample, when a single sidelink resource is selected, the transmittingterminal may select a DMRS pattern configured by being mapped to theselected sidelink resource. Alternatively, the transmitting terminal mayselect the DMRS pattern on the basis of property information of theselected sidelink resource.

For example, the selected predetermined DMRS pattern may be determinedon the basis of information regarding consecutive symbols of a sidelinkresource selected for transmission of a physical sidelink shared channel(PSSCH), information regarding the number of symbols to which a physicalsidelink control channel (PSCCH) is allocated, and information regardingthe number of symbols of a DMRS included in the PSSCH. Specifically,when a PSSCH sidelink resource, via which sidelink data is to betransmitted, is selected, information regarding consecutive symbols ofthe corresponding PSSCH sidelink resource, the number of symbols of thePSCCH allocated in a slot in which the PSSCH is transmitted, and thenumber of DMRS symbols may be determined. In this case, the position ofa symbol, through which the DMRS is to be transmitted, may be determinedaccording to combinations of respective situations, on the basis ofpreviously-configured information in the form of a table. For example,the information regarding the number of symbols to which the PSCCH isallocated may be set to be 2 or 3, and the information regarding thenumber of symbols of the DMRS included in the PSSCH may be set to be 2,3, or 4. That is, respective construction factors may be determined forthe respective sidelink resources in the above-described number range.

The transmitting terminal may perform an operation of transmitting thePSCCH and the PSSCH in a single slot using the selected sidelinkresource and transmitting the DMRS in a predetermined symbol of thePSSCH on the basis of the predetermined DMRS pattern. For example, whenthe sidelink resource for the transmission of the sidelink data isdetermined, the transmitting terminal may transmit the PSCCH and thePSSCH in a single slot. The DMRS pattern information included in thePSSCH may be indicated to the receiving terminal as sidelink controlinformation (SCI).

For example, predetermined DMRS pattern information applied to the PSSCHmay be indicated by a DMRS pattern filed of the SCI included in thePSCCH. The DMRS pattern filed may be included in first SCI and bedetermined to be one value from among 1 to 5 bits. Alternatively, thebit value of the DMRS pattern filed may be determined depending on anumber value of the DMRS pattern information transmitted by the basestation. An SCI format including a DMRS pattern indicator field is SCI0_1.

The receiving terminal may receive the sidelink data in the PSSCHsidelink resource indicated by the PSCCH and review DMRS symbolsallocated in the PSSCH region using the DMRS pattern indicator field.

When a pattern table regarding DMRS allocation symbols is configured inthe transmitting terminal and the receiving terminal, the DMRS patterninformation included in the DMRS pattern indicator field may includeinformation indicating the number of DMRS patterns allocated to thePSSCH. That is, since the number of consecutive symbols of the PSSCH andthe number of symbols configured with the PSCCH may be reviewed viaother fields of the SCI, when the DMRS number information is reviewed,the receiving terminal may review information regarding the symbols, towhich the DMRS is allocated, using the table. In this case, the DMRSindicator field may be comprised of 2 bits.

According to the above-described operations, the transmitting terminalperforms transmission by dynamically configuring the DMRS patterns, andthe receiving terminal may receive the PSSCH by reviewing thedynamically configured DMRS patterns.

Next, synchronization signal transmitting and receiving operations forperforming sidelink communication in a case in which synchronizationconfiguration based on the base station is applied will be described.

In sidelink communications, an allocated frequency range may be set tobe relatively narrow in a number of cases, unlike the case of the Uuinterface. There may be more cases in which information must betransmitted through a broadcast channel. In addition, slot-basedtransmission of the synchronization signal is required.

Thus, the present disclosure proposes a sidelink synchronization signalblock (S-SSB) different from the synchronization signal block (SSB) inthe Uu interface.

The terminal may perform an operation of receiving the configurationinformation regarding the SSB including synchronization information forsidelink communications.

For example, the S-SSB configuration information may include at leastone from among subcarrier index information of a frequency domain inwhich S-SSBs are transmitted, information regarding the number of S-SSBstransmitted within the period of a single sidelink synchronizationsignal, offset information from a start point of the period of thesidelink synchronization signal to a first S-SSB monitoring slot, andinterval information between S-SSB monitoring slots. In an example, theperiod of the sidelink synchronization signal may be configured to be 16frames and to be 160 ms. In another example, the period of the sidelinksynchronization signal may be configured to be 16 multiples.

In another example, the number of S-SSBs may be set to be within adifferential range according to the subcarrier spacing set to afrequency range in which the S-SSB is transmitted. The subcarrierspacing in the frequency range may be configured to be 15, 30, 60, 120,and 240 kHz, as illustrated in Table 1. Specifically, when thesubcarrier spacing is 15 kHz, the number of S-SSBs is set to be 1 or 2.Alternatively, when the subcarrier spacing is 30 kHz, the number ofS-SSB is set to be 1, 2, or 4. Alternatively, when the subcarrierspacing is 60 kHz, the number of S-SSB is set to be one from among 1, 2,4, and 8. Alternatively, when the subcarrier spacing is 120 kHz, thenumber of S-SSB is set to be one from among 1, 2, 4, 8, 16, 32, and 64.In addition, in the case of FR2, even when the subcarrier spacing is setto be 60 kHz, the number of S-SSBs may be set to be one from among 1, 2,4, 8, 16, and 32.

The terminal may perform an operation of monitoring a configured S-SSBmonitoring slot on the basis of the S-SSB configuration information. Forexample, the terminal monitors a predetermined slot in the period of thesidelink synchronization signal on the basis of the S-SSB configurationinformation.

For example, when 16 frames are configured in a period of the sidelinksynchronization signal, the spacing from a start slot of the period ofthe sidelink synchronization signal to a first S-SSB monitoring slot ofthe period of the synchronization signal is reviewed, on the basis ofthe offset information. In addition, the terminal reviews the spacingfrom the first S-SSB monitoring slot to a second S-SSB monitoring slotusing the interval information. In the same manner, the spacing from thesecond S-SSB monitoring slot to a third S-SSB monitoring slot isreviewed using the interval information. In addition, the terminalcounts the number of the entire S-SSB monitoring slots allocated in theperiod of the sidelink synchronization signal using the informationregarding the number of the S-SSBs. Thus, the terminal reviews andmonitors the index (or position) of the monitoring slot in the period ofthe sidelink synchronization signal using the S-SSB configurationinformation.

The terminal may perform an operation of receiving the S-SSB in theS-SSB monitoring slot. For example, the terminal receives the S-SSB inthe monitoring slot using the above-described S-SSB configurationinformation. The S-SSB is comprised of a sidelink primarysynchronization signal (S-PSS), a sidelink secondary synchronizationsignal (S-SSS), and a physical sidelink broadcast channel (PSBCH). TheS-PSS, the S-SSS, and the PSBCH may be allocated to N number ofconsecutive symbols in the S-SSB monitoring slot.

FIG. 12 is a diagram illustrating an example of an S-SSB allocated in anS-SSB monitoring slot according to an embodiment.

Referring to FIG. 12 , the S-SSB may be allocated to N number ofconsecutive symbols in the S-SSB monitoring slot. In this case, theS-SSB may be comprised of two S-PSS symbols, two S-SSS symbols, and N−4number of PSBCH symbols. For example, the S-SSB may be configured suchthat the PSBCH is allocated to symbol index 0 in the S-SSB monitoringslot, the S-PSS is allocated to symbol indices 1 and 2 in the S-SSBmonitoring slot, the S-SSS is allocated to symbol indices 3 and 4 in theS-SSB monitoring slot, and the PSBCH is allocated to symbol indices 5 toN−1 in the S-SSB monitoring slot. In this case, when the S-SSBmonitoring slot is a normal cyclic prefix (CP), N is 13. When the S-SSBmonitoring slot is an extended CP, N is 11. That is, when a single slotis comprised of 14 or 12 symbols, the S-SSB may be configured byallocating the S-PSS, the S-SSS, and the PSBCH to the symbols, exceptfor the last symbol. In another example, the S-SSB may be comprised of132 subcarriers.

In addition, also in sidelink communications, an HARQ operation may beperformed. However, there is a problem in that the HARQ operationfrequently performed in sidelink communications causes the overlappingof resources and increased system load. In addition, the HARQ operationmay not be properly performed due to the limited transmission power ofthe terminal.

Therefore, the present disclosure proposes the HARQ operation of theterminal.

FIG. 13 is a diagram illustrating operations of a terminal according toan embodiment.

Referring to FIG. 13 , in a method of controlling a sidelink HARQfeedback operation, the terminal may perform an operation of receivinggroup-cast sidelink data from the transmitting terminal through thephysical sidelink shared channel (PSSCH) in S1300.

For example, the terminal receives a physical sidelink control channel(PSCCH) and the PSSCH from the transmitting terminal. Sidelinkcommunications may support unicast communication between terminals,groupcast communication between a single transmitting terminal andplurality of receiving terminals in a group, and broadcast communicationin which a single transmitting terminal performs broadcasting.

In the case of groupcast communication, the PSCCH may include schedulinginformation regarding a PSSCH wireless resource including sidelinkgroupcast data. The terminal receives the PSSCH including groupcastsidelink data on the basis of the SCI included in the PSCCH.

In S1310, the terminal may perform an operation of determining whetheror not to transmit HARQ feedback information of groupcast sidelink dataon the basis of the position information of the transmitting terminal.

For example, the position information of the transmitting terminal maybe included in sidelink control information (SCI) received through thePSSCH, and may include zone ID information of the transmitting terminal.The SCI received through the PSSCH may mean second SCI. That is, the SCIreceived through the PSSCH is different from SCI received through thePSCCH including scheduling information regarding the groupcast sidelinkdata. For example, the SCI received through the PSSCH may include HARQprocess ID information, new data indicator information, redundancyversion information, transmitting terminal ID information, receivingterminal ID information, CSI request information, zone ID information,and communication range request information.

In addition, geographic position information mapped according to thezone ID information may be received from the base station by higherlayer signaling. The terminal may obtain the position information of thetransmitting terminal using the geographic position informationaccording to the zone ID information received from the base station andthe zone ID information of the transmitting terminal.

In addition, the HARQ feedback information may be determined on thebasis of distance information calculated according to the position ofthe transmitting terminal and the position of the terminal and on thebasis of whether or not the decoding of the groupcast sidelink data hassucceeded.

In an example, only when the decoding of the groupcast sidelink data hasfailed and the distance information is equal to or less than apredetermined threshold value, it may be determined to transmit the HARQfeedback information. The HARQ feedback information may includeHARQ-NACK information.

In another example, when the distance information is equal to or greaterthan the predetermined threshold value, it may be determined to transmitthe HARQ feedback information including HARQ-ACK information orHARQ-NACK information depending on whether or not the decoding of thegroupcast sidelink data has succeeded.

In a further example, when the decoding of the groupcast sidelink datahas succeeded, it may be determined not to transmit the HARQ feedbackinformation irrespective of the distance information.

In yet another example, only when the decoding of the groupcast sidelinkdata has failed, it may be determined whether or not to transmit theHARQ feedback information on the basis of the distance information.

The above-described transmission of the HARQ feedback information may beonly performed when the sidelink HARQ feedback operation is activated.That is, the sidelink HARQ feedback operation may be activated ordeactivated, and whether to activate or deactivate the sidelink HARQfeedback operation may be determined by a command from the base stationor the transmitting terminal. In addition, the above-described thresholdvalue may be included in the SCI (e.g., communication range requestinformation) received through the PSSCH or may be provided in theterminal by the base station.

In S1320, when it is determined to transmit the HARQ feedbackinformation, the terminal may perform an operation of transmitting theHARQ feedback information.

For example, when it is determined to transmit the HARQ feedbackinformation, the terminal may transmit the HARQ feedback informationregarding the groupcast sidelink data.

The above-described operations provide effects that unnecessary sidelinksystem load may be reduced and the HARQ feedback operation may beperformed based on the distance information between the transmittingterminal and the terminal.

FIG. 14 is a diagram illustrating SCI received through the PSCCHaccording to an embodiment.

Referring to FIG. 14 , the SCI may be transmitted through the PSCCH andthe PSSCH. The SCI transmitted through the PSCCH may include PSCCHscheduling information and the like, and be described as being firstSCI.

For example, the first SCI includes a priority field regarding priority,a frequency resource allocation (or assignment) field regarding thePSSCH, and a time resource allocation (or assignment) field. In case ofresource reservation, resource reservation period information isincluded. In addition, the first SCI may include the above-describedDMRS pattern indicator field. In addition, the first SCI may include aformat field indicating a second SCI format, a beta offset indicatorfield, a field indicating the number of DMRS ports, and a fieldindicating modulation and a coding scheme. Among these, the size of thefrequency and resource reservation period field may be variably set. ADMRS pattern field and a second SCI format field may be fixed topredetermined bits or may be variably configured. The receiving terminalmay review the DMRS pattern information by receiving the first SCIillustrated in FIG. 14 .

FIG. 15 is a diagram illustrating SCI received through the PSSCHaccording to an embodiment.

Referring to FIG. 15 , the second SCI received through the PSSCH mayinclude K-bit fields including HARQ process ID information. In addition,the second SCI may include a one-bit new data indicator field indicatingwhether the data of the PSSCH is retransmission data or initialtransmission data. In addition, the second SCI may include a two-bitredundancy version field for the HARQ process. In addition, the secondSCI may include a source ID field including identification informationof the transmitting terminal that has transmitted the PSSCH. Thecorresponding filed is comprised of eight bits. In addition, the secondSCI may include a 16-bit destination ID field including destinationidentification information of the PSSCH. In addition, the second SCI mayinclude a one-bit CSI request field requesting channel state informationand a four-bit communication range request field. In addition, an N-bitzone ID field including the position information of the transmitterterminal described above may be included.

Hereinafter, a variety of embodiments for calculating distanceinformation between the transmitting terminal and the receiving terminalwill be described with reference to the drawings.

FIG. 16 is a diagram illustrating operations of calculating distanceinformation on the basis of the positions of a transmitting terminal anda terminal according to an embodiment.

Referring to FIG. 16 , a transmitting terminal (UE) Tx may not considerthe position of a receiving terminal (UE) Rx. In this case, thetransmitting terminal may transmit SCI including position informationobtained by the GNSS or a base station. The receiving terminal mayobtain the position information of the transmitting terminal from thereceived SCI. For example, the position information of the transmittingterminal may be transmitted by identification information in whichgeographical positions are divided in the form of zones.

In an example, when the identification information of the geographicalposition of the transmitting terminal is 1111 and the identificationinformation of the geographical position of the receiving terminal is1110, the transmitting terminal may transmit the SCI including four-bitzone identification information indicating 1111.

In another example, when the transmitting terminal is aware of theposition of the receiving terminal, the transmitting terminal maytransmit the SCI including relative position information of thetransmitting terminal with respect to the receiving terminal. Here, therelative position information of the transmitting terminal may use nnumber of bits, and the SCI may include resolution information of theposition information. FIG. 16 illustrates an example in which four bitsare used and resolution is 10m×10m. In this scenario, the transmittingterminal may transmit information including the relative positioninformation of 1110 and the resolution information of 1110.

In yet another example, when GNSS information is not used, the receivingterminal may determine whether or not to perform an HARQ feedbacktransmission by calculating the distance between the transmittingterminal and the receiving terminal by considering the intensity of thesignal and sidelink path loss and comparing the distance with acommunication request range.

CQI, PMI, RI, and the like, indicating the channel state, arecharacterized by varying depending on the degree of fading. The fadingmeans a phenomenon in which two or more radio waves having differentpaths interfere with each other, so that the signal amplitudes, phases,and the like thereof irregularly change over time. In particular,small-scale fading occurs due to the combination of a plurality ofmulti-paths reflection waves generated by the influence of surroundingstructures, and is characterized by rapidly changing in a short time.The degree of fading is directly related to a path loss factor in anon-line-of-sight (NLOS) situation, and is closely related to measuredvalues of CQI, PMI, and RI. Thus, after the path loss factor isestimated from the CQI, PMI, RI, and the like, a more accurate distancemay be calculated using reference signal received power (RSRP) andreference signal transmission power (RSTP). The relationship among thedistance between transmitting and receiving ports, the RSRP, and theRSTP, and the path loss factor may be determined by a predeterminedformula.

FIG. 17 is a diagram illustrating operations of receiving the positioninformation of a transmitting terminal according to an embodiment.

Referring to FIG. 17 , the transmitting terminal may transmit theposition information thereof on the basis of zone IDs. In this case,geographic position information corresponding to the zone IDs mayconfigured in the form of a table in advance by the transmittingterminal and a receiving terminal.

For example, the zone IDs may be configured in the form of a table onthe basis of geometrical zones. The configured zone IDs in the form of atable are stored in advance by the transmitting terminal and thereceiving terminal. When a zone ID is received, the receiving terminalmay review the geographic position information of the transmittingterminal. Since the geographic position information of the receivingterminal may be estimated by receiving a GNSS signal or a base stationreference signal of the receiving terminal, when the receiving terminalis aware of the geographic position information of the transmittingterminal, the receiving terminal may calculate the distance informationbetween the transmitting terminal and the receiving terminal.

Here, the respective zones and IDs corresponding to the zones may bedefined in advance as rectangular blocks as illustrated in FIG. 17 .When the position of a transmitting vehicle obtained using the GPS iswithin one of the previously defined zones, the transmitting terminaldetermines the ID of the corresponding zone as the zone ID of thetransmitting terminal. The determined zone ID may be transmitted bybeing included the SCI so as to be used in the determination of HARQfeedback of the receiving terminal.

FIG. 18 is a diagram illustrating operations of receiving the positioninformation of a transmitting terminal according to another embodiment.

Referring to FIG. 18 , zone IDs may be determined on the basis ofcommunications coverage of a base station. Here, terminals 1800 havezone IDs based on the base station, respectively. When a specificterminal 1800 is performing a communication by RRC connection with gNB4,the zone ID of the terminal 1800 may be determined to be zone ID #4corresponding to gNB4. That is, the zone IDs may be determined accordingto the base station. In this case, the terminal may transmit SCIincluding information indicating zone ID #4.

<<FIG. 19 is a diagram illustrating position information of atransmitting terminal according to another embodiment.

Referring to FIG. 19 , respective zones and zone IDs corresponding tothe zones may be defined in advance as non-uniform zones. The sizes ofthe zones are determined by a higher layer in consideration of thedensity of terminals and the accuracy of positioning according to thezones. Information regarding the zone IDs of terminals located in thecell of at least one or more base station or in a specific range may beconfigured in advance in the respective terminals. When a transmittingterminal 1900 is located in a specific zone, a corresponding vehicletransmits SCI including the ID of the corresponding zone. For example,when the terminal 1900 is located in zone #5, the terminal transmits theSCI including information indicating #5.

In addition, the zone ID and the communication range may be included asK and 4 bits in second stage SCI. As described above, zone IDinformation may be used to calculate a distance between a transmitterand a receiver (i.e. a Tx-Rx distance). The communication range may beused as a threshold value for HARQ feedback transmission based on theTX-RX distance.

The receiving terminal calculates TX-RX distance information using theposition thereof and the zone ID of the transmitting terminal. Thecalculated TX-RX distance information may be compared with thecommunication range for use in determination of whether or not toperform an HARQ feedback operation. In an example, in a groupcastsituation, when a TX-RX distance calculated by a receiving terminal isgreater than the communication range, the corresponding terminal doesnot send an ACK or a NACK of an HARQ operation. In the opposite case,the terminal sends an ACK or a NACK. That is, when the TX-RX distanceinformation is calculated using the zone ID and the position of thereceiving terminal, whether or not to transmit an HARQ feedback signalmay be finally determined by comparing the calculated TX-RX distanceinformation with communication range information that may be included inthe SCI. Although the communication range information has been describedas being included in the SCI as described above, a predetermined tablemay be defined in advance, and the communication range information mayonly include an indicator value for identifying the table. In addition,the communication range information may be shared by the terminals byhigher layer signaling. That is, the base station may transmit thecommunication range to the respective terminals, so that whether or notto perform the HARQ feedback operation may be determined using thecommunication range before a predetermined time or the occurrence of apredetermined event.

FIG. 20 is a diagram illustrating a configuration of a terminalaccording to an embodiment.

Referring to FIG. 20 , a terminal 2000 controlling a sidelink HARQfeedback operation may include a receiver 2030, a controller 2010, and atransmitter 2020. The receiver 2030 receives groupcast sidelink datathrough a physical sidelink shared channel (PSSCH). The controller 2010determines whether or not to transmit groupcast sidelink data and HARQfeedback information, on the basis of the position information of atransmitting terminal. When it is determined to transmit the HARQfeedback information, the transmitter 2020 transmits the HARQ feedbackinformation.

For example, the receiver 2030 receives a physical sidelink controlchannel (PSCCH) and the PSSCH from the transmitting terminal. Sidelinkcommunications may support unicast communication, i.e. one-to-onecommunication between terminals, groupcast communication between asingle transmitting terminal and plurality of receiving terminals in agroup, and broadcast communication in which a single transmittingterminal performs broadcasting. In the case of groupcast communication,the PSCCH may include scheduling information regarding a PSSCH wirelessresource including sidelink groupcast data. The receiver 2030 receivesthe PSSCH including groupcast sidelink data on the basis of sidelinkcontrol information (SCI) included in the PSCCH.

In addition, the position information of the transmitting terminal maybe included in the SCI received through the PSSCH, and may include zoneID information of the transmitting terminal. The SCI received throughthe PSSCH may mean second SCI. That is, the SCI received through thePSSCH is different from SCI received through the PSCCH includingscheduling information regarding the groupcast sidelink data. Forexample, the SCI received through the PSSCH may include HARQ process IDinformation, new data indicator information, redundancy versioninformation, transmitting terminal ID information, receiving terminal IDinformation, CSI request information, zone ID information, andcommunication range request information.

In addition, geographic position information mapped according to thezone ID information may be received from a base station by higher layersignaling. The controller 2010 may obtain the position information ofthe transmitting terminal using the geographic position informationaccording to the zone ID information received from the base station andthe zone ID information of the transmitting terminal.

In addition, the HARQ feedback information may be determined on thebasis of distance information calculated according to the position ofthe transmitting terminal and the position of the terminal and on thebasis of whether or not the decoding of the groupcast sidelink data hassucceeded. In an example, only when the decoding of the groupcastsidelink data has failed and the distance information is equal to orless than a predetermined threshold value, it may be determined totransmit the HARQ feedback information. The HARQ feedback informationmay include HARQ-NACK information. In another example, when the distanceinformation is equal to or greater than the predetermined thresholdvalue, it may be determined to transmit the HARQ feedback informationincluding HARQ-ACK information or HARQ-NACK information depending onwhether or not the decoding of the groupcast sidelink data hassucceeded. In a further example, when the decoding of the groupcastsidelink data has succeeded, it may be determined not to transmit theHARQ feedback information irrespective of the distance information. Inyet another example, only when the decoding of the groupcast sidelinkdata has failed, it may be determined whether or not to transmit theHARQ feedback information on the basis of the distance information.

The above-described transmission of the HARQ feedback information may beonly performed when the sidelink HARQ feedback operation is activated.That is, the sidelink HARQ feedback operation may be activated ordeactivated, and whether to activate or deactivate the sidelink HARQfeedback operation may be determined by a command from the base stationor the transmitting terminal. In addition, the above-described thresholdvalue may be included in the SCI (e.g., communication range requestinformation) received through the PSSCH or may be provided in theterminal by the base station.

When it is determined to transmit the HARQ feedback information, thetransmitter 2020 may transmit the HARQ feedback information regardingthe groupcast sidelink data.

In addition, the controller 2010 may control the operations of theterminal 2000 required for performing the foregoing embodiments.

In addition, the transmitter 2020 and the receiver 2030 serve totransmit and receive signals, data, and messages to and from the basestation and other terminals through corresponding channels.

Embodiments of the present disclosure may be supported by standarddocuments of at least one of the IEEE 802 system, the 3GPP system, andthe 3GPP2 system, all of which are wireless access systems. That is,steps, components, or portions not described in embodiments of thepresent disclosure for the sake of clearly describing the spirit of thepresent disclosure may be supported by the standard documents. For allterms used herein, reference may be made to the standard documents.

Embodiments of the present disclosure may be implemented using a varietyof means. For example, embodiments of the present disclosure may beimplemented using hardware, firmware, software, or any combinationthereof.

In the case in which the present disclosure is implemented usinghardware, the methods according to embodiments of the present disclosuremay be realized using one or more application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSPDs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, or the like.

In the case in which the present disclosure is implemented usingfirmware or software, the methods according to embodiments of thepresent disclosure may be implemented in the form of devices, processes,functions, or the like performing the functions or operations describedabove. Software codes may be stored in a memory unit so as to beexecuted by a processor. The memory unit may be located inside oroutside of the processor and may exchange data with the processor via avariety of known means.

The terms, such as “system”, “processor”, “controller”, “component”,“module”, “interface”, “model”, or “unit”, used herein may generallyrefer to computer-related entity hardware, a combination of hardware andsoftware, software, or software in execution. For example, theabove-described components may be at least one selected from among, butnot limited to, a process, a processor, a controller, a controlprocessor, an entity, an execution thread, a program, and a computer.For example, both an application being executed by the controller orprocessor and the controller or processor may be a component. One ormore components may reside in at least one of a process and an executionthread. A component may be located in a single device (e.g. a system ora computing device) or may be distributed to two or more devices.

The foregoing descriptions have been presented in order to explaincertain principles of the present disclosure by way of example. Thosehaving ordinary knowledge in the technical field to which the presentdisclosure relates could make various modifications and variationswithout departing from the essential features of the principle of thepresent disclosure. In addition, the foregoing embodiments shall beinterpreted as being illustrative, while not being limitative, of theprinciple and scope of the present disclosure. It should be understoodthat the scope of protection of the present disclosure shall be definedby the appended Claims and all of their equivalents fall within thescope of protection of the present disclosure.

The invention claimed is:
 1. A method of controlling a sidelink hybridautomatic repeat request (HARQ) feedback operation by a terminal, themethod comprising: receiving groupcast sidelink data from a transmittingterminal through a physical sidelink shared channel (PSSCH); determiningwhether or not to transmit HARQ feedback information of the groupcastsidelink data in accordance with position information of thetransmitting terminal; and when it is determined to transmit the HARQfeedback information, transmitting the HARQ feedback information,wherein the position information of the transmitting terminal isincluded in sidelink control information received through the PSSCH andincludes zone ID information of the transmitting terminal, wherein thezone ID information is determined, by the transmitting terminal, basedon higher layer signaling received from a base station, wherein thesidelink control information received through the PSSCH is differentfrom sidelink control information received through a physical sidelinkcontrol channel (PSCCH) including scheduling information regarding thegroupcast sidelink data, wherein the sidelink control informationreceived through the PSCCH includes a priority field regarding priority,a frequency resource allocation field regarding the PSSCH, a timeresource allocation field, and demodulation reference signal (DMRS)pattern indicator field, wherein the DMRS pattern indicator fieldindicates predetermined DMRS pattern, and wherein the predetermined DMRSpattern is determined in accordance with information regardingconsecutive symbols of a sidelink resource selected for transmission ofthe PSSCH, information regarding the number of symbols to which thePSCCH is allocated, and information regarding the number of symbols of aDMRS included in the PSSCH.
 2. The method according to claim 1, whereinthe HARQ feedback information is determined in accordance with distanceinformation calculated according to the position information of thetransmitting terminal and position information of the terminal and inaccordance with whether or not decoding of the groupcast sidelink datahas succeeded.
 3. The method according to claim 2, wherein, only whenthe decoding of the groupcast sidelink data has failed and the distanceinformation is equal to or less than a predetermined threshold value,the HARQ feedback information is determined to be transmitted, andincludes HARQ negative acknowledgement (HARQ-NACK) information.
 4. Themethod according to claim 2, wherein, when the decoding of the groupcastsidelink data has succeeded, it is determined not to transmit the HARQfeedback information irrespective of the distance information.
 5. Aterminal for controlling a sidelink hybrid automatic repeat request(HARQ) feedback operation, the terminal comprising: a receiver receivinggroupcast sidelink data from a transmitting terminal through a physicalsidelink shared channel (PSSCH); a controller determining whether or notto transmit HARQ feedback information of the groupcast sidelink data inaccordance with position information of the transmitting terminal; and atransmitter transmitting the HARQ feedback information when it isdetermined to transmit the HARQ feedback information, wherein theposition information of the transmitting terminal is included insidelink control information received through the PSSCH and includeszone ID information of the transmitting terminal, wherein the zone IDinformation is determined based on higher layer signaling received froma base station, wherein the sidelink control information receivedthrough the PSSCH is different from sidelink control informationreceived through a physical sidelink control channel (PSCCH) includingscheduling information regarding the groupcast sidelink data, whereinthe sidelink control information received through the PSCCH includes apriority field regarding priority, a frequency resource allocation fieldregarding the PSSCH, a time resource allocation field, and demodulationreference signal (DMRS) pattern indicator field, wherein the DMRSpattern indicator field indicates predetermined DMRS pattern, andwherein the predetermined DMRS pattern is determined in accordance withinformation regarding consecutive symbols of a sidelink resourceselected for transmission of the PSSCH, information regarding the numberof symbols to which the PSCCH is allocated, and information regardingthe number of symbols of a DMRS included in the PSSCH.
 6. The terminalaccording to claim 5, wherein the HARQ feedback information isdetermined in accordance with distance information calculated accordingto the position information of the transmitting terminal and positioninformation of the terminal and in accordance with whether or notdecoding of the groupcast sidelink data has succeeded.
 7. The terminalaccording to claim 6, wherein, only when the decoding of the groupcastsidelink data has failed and the distance information is equal to orless than a predetermined threshold value, the HARQ feedback informationis determined to be transmitted, and includes HARQ negativeacknowledgement (HARQ-NACK) information.
 8. The terminal according toclaim 6, wherein, when the decoding of the groupcast sidelink data hassucceeded, it is determined not to transmit the HARQ feedbackinformation irrespective of the distance information.